Still has a flathead V8? I've seen some that get "starter bind" . Try rocking the motor back and forth to see if the starter gear is bound up on the flywheel gear. If it was stuck, it could be that the front bracket on the starter is missing.

^^^^^^
What he said - - - I had a 49 sedan flathead 6 that did that all the %#$#&%%#$ time and rocking always did the trick